A steel pipe may be blocking Bertha

By LYNSI BURTON, SEATTLEPI.COM STAFF

Updated 11:23 pm, Friday, January 3, 2014

Bertha had cleared about 370 feet of tunnel when this state Department of Transportation photo was taken Thursday, Oct. 24, 2013. (DEPARTMENT OF TRANSPORTATION)
Photo: Multiple

Bertha had cleared about 370 feet of tunnel when this state...

The cutter head of the Washington State Department of Transportation's Big Bertha Highway 99 tunnel boring machine is lowered into its launch pit on Friday, May 31, 2013. . (JOSHUA TRUJILLO, SEATTLEPI.COM)
Photo: Multiple

The cutter head of the Washington State Department of...

Workers and officials pose for a photo as the cutter head of the Washington State Department of Transportation's Big Bertha Highway 99 tunnel boring machine is lowered into its launch pit on Friday, May 31, 2013. (Photo by Joshua Trujillo, seattlepi.com)

A steel pipe may be blocking Bertha, the machine that is digging the tunnel to replace the Alaskan Way Viaduct.

Officials indicated that the pipe was put there in 2002 by state Department of Transportation contractors and that Bertha ran into the pipe days before it ground to a halt.

The machine stopped Dec. 6 after it met an obstruction, reported at the time to be an unknown problem. Officials said Friday they found an 8-inch diameter steel pipe in the way.

Crews lowered the water table underground around Bertha and drilled borings three feet in front of the head of the machine. Six of the 12 borings revealed obstructions in front of the machine. They were able to look inside the top portion of the machine's cutting head Thursday night and found that the pipe may be its obstruction.

The wear and tear on Bertha's cutting tools were "very unusual for the type of ground we're going through," said Chris Dixon, project manager with Seattle Tunnel Partners.

More investigation has yet to be done to see whether there are other causes of Bertha's halt.

The pipe was put there by contractors for the transportation department who were performing viability tests for a possible viaduct replacement following the 2001 Nisqually earthquake that damaged the viaduct.

Furthermore, the pipe's location was included in reference materials in the tunnel-boring contract.

But the pipe may not be the only problem:

"Other potential factors include changing soil conditions that may have caused excessive wear of cutting tools, potential objects in front of the cutterhead or objects in the lower portion of the excavation chamber that still aren't visible," according to a written statement by the Department of transportation.

Bertha mined through the steel pipe three to four days before it stopped moving, officials said. The pipe came 6 to 7 feet out of the ground and crews removed it. However, more of the pipe was still underground.

Consultants assured the Department of Transportation that what remained of the pipe would not be an issue moving forward. When Bertha stopped, they didn't guess it was because of the pipe.

"At that point in time, we were pretty convinced (the culprit) was something else," said Matt Preedy, deputy administrator of the Alaskan Way Viaduct Replacement Program.

Officials declined to comment on how long the current delay might last, only saying that they're exploring options on how to further investigate the problem.

"We don't want to push this thing 'til we know once and for all the extent of the issue," Preedy said.

Likewise, they did not hazard a guess on how much money this delay is costing.

Sitting somewhere between South Main Street and South Jackson Street, Bertha is 10 percent, or about 1,000 feet, into its planned path. The viaduct replacement tunnel is supposed to open sometime next year.

This is the third hold-up since Bertha began drilling in July. It follows stoppages for a union labor strike and a sinkhole near South Jackson Street.